In the mining industry are used transportation devices with ropes. The loads are lifted or lowered by means of a load platform or a hoisting cage and with regard to safety reasons with a plurality of steel cables. The parallel connected cables have the purpose that in the case of breaking of one cable the load is held by the remaining cables.
Today it is possible to expand with vertical transportation devices into depths of about 4000 m.
It is also possible to lift loads up to 3000 tons.
Also conveying velocities up to 20 m/s may be achieved.
With transportation devices with ropes these three maxima are not applicable in an additive way.
It is also known that cables may break suddenly because they are exposed to a continuous deterioration, a deformation and in particular an exposure to varying loads.
In the bearer cable technology are used winches on which the cables are recoiled and uncoiled, respectively.
The driving motors of the winches are complemented by technical safety installations in order that in the case of a failure of the driving motors, for example during a power breakdown, the speed can be diminished in a controlled way to “zero” and the load can be held permanently in this slowed down status.
This additional effort in transportation devices with ropes is not safe enough for the lifting and lowering of containers with radioactive contents having a weight of up to 120 tons.
Hoisting devices that use the known principle of the so-called spindle/worm wheel combination do not have these disadvantages.
There exist two different kinds of spindle hoisting gears.
Either the spindles revolve and the worm wheels are trapped in the load platform or the worm wheels turn around the fixed spindles.
In both of these spindle hoisting gears are possible only conveyer heights in the range from only 15 m to 20 m.
This is due to the buckling loads occurring in the spindles at longer conveyer heights and constant diameter of the spindles.